ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1
f. Magnetic Shapes. Because of the many uses of magnets, they
are found in various shapes and sizes. However, magnets usually
come under one of three general classifications: bar magnets,
horseshoe magnets, or ring magnets.
(1) Bar Magnets. The bar magnet is most often used in schools
and laboratories for studying the properties and effects of
magnetism. In the preceding material, the bar magnet proved
very helpful in demonstrating magnetic effects.
(2) Horseshoe Magnets. The shape of the magnet most
frequently used in electrical and electronic equipment is called
the horseshoe magnet. A horseshoe magnet is similar to a bar
magnet but is bent in the shape of a horseshoe. The horseshoe
magnet provides much more magnetic strength than a bar magnet of
the same size and material because of the closeness of the
magnetic poles. The magnetic strength from one pole to another
is greatly increased due to the concentration of the magnetic
field in a similar area. Electrical measuring devices quite
frequently use horseshoetype magnets.
(3) Ring Magnets. Another type of magnet is the ring magnet,
which is used for computer memory cores. A common application
for a temporary ring magnet would be the shielding of electrical
instruments.
g. Care of Magnets. A piece of steel that has been magnetized
can lose much of its magnetism by improper handling. If it is
jarred or heated, there will be a disalignment of its domains,
resulting in the loss of some of its effective magnetism. Had
this piece of steel formed the horseshoe magnet of a meter, the
meter would no longer be operable or would give inaccurate
readings. Therefore, care must be exercised when handling
instruments containing magnets. Severe jarring or subjecting
the instrument to high temperatures will damage the device.
A magnet may also become weakened from loss of flux. Thus, when
storing magnets, one should always try to avoid excess leakage
of magnetic flux. A horseshoe magnet should always be stored
with a keeper, a soft iron bar used to join the magnetic poles.
By using the keeper when the magnet is stored, the magnetic flux
will
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